So with a little encouragement from Mitt, Marco and Ted finally stood up to The Donald in Houston – eight months after he launched his campaign. While others debate the question of whether it’s too little too late, let us speculate here on the reasons why almost no one – including but especially his opponents – dared to step into the ring with the bloviating billionaire bully until now.

They flat out under-estimated him until it was too late to do much about it.

In a political campaign, under-estimating your opponent is the only mistake worse than over-estimating him. Nobody in the pundit class or the political professional sector really took his candidacy seriously until Iowa – even though he has a campaign manager who cut his teeth with the RNC and the Koch Brothers’ machine, and a coterie of second-tier wise guys with decades of experience going back to Lee Atwater and Richard Nixon.

He has something on them.

Maybe it’s an embarrassing photo, or a scandalous video, or just the personal knowledge of such a damning piece of evidence. More than a few people have been silenced or coerced into dropping their candidacy or their opposition to a candidate because of their own indiscretions. Because he’s both shameless and brutish, Trump would not hesitate to expose that kind of information, no matter who it hurts, and they know it.

They owe him.

They’re beholden to him because of the money he has poured into their campaign coffers over the years.

This applies both to candidates and to donors: the candidates because they have benefitted directly, and the donors because they were collaborators and profited indirectly. In addition, there’s a weird kind of honor code at work here, and once again, it gives Trump an advantage.

They’re cowards.

They saw what happened to Rick Perry, Bobby Jindal, Carly Fiorina and others who tried to take him on, including some media types, and they’re afraid it could happen to them. People in elected office are afraid for obvious reasons, but the donors who shrink from the challenge are probably responding more to peer pressure and fear of losing face.

They don’t want to deal themselves out of the game if he ends up with the nomination.

Most people in this business just want (or need) to be in it – one way or another, whatever it takes, no matter who they have to sleep with. Because Trump is so vicious, there’s a good chance he wouldn’t allow them to kiss and make up afterward if they go against him. And because he’s so volatile, there’s no reason to believe he wouldn’t turn on them afterward if he did.

Whatever the reasons, as Edmund Burke might remind then, the powers that be in the GOP have no one but themselves to blame for Trump’s ascendancy.

(Note: This was written before Chris Christie endorsed Trump. At least two of these are possibilities where he’s concerned – and for those who are about to follow him.)